Stress proteins are known to play essential roles in normal cellular functions and in protecting cells from stress, e.g., in thermotolerance. Several of these proteins have come under intense scrutiny. However, from the earliest studies, major stress proteins known as hsp110 (in the cytoplasm) and grp170 (in the endoplasmic reticulum) were observed, but studies of their structure and function were not undertaken; that is, until recently. Recent cloning of these proteins in the laboratory of the P.I. indicated that they are related to one another and are also distant relatives of the intensively studied hsp70 family. Moreover, they have been observed in every eukaryotic cell examined, from yeast to man. Since these conserved stress proteins reside in parallel with members of the hsp70 family in both the cytoplasm and the endoplasmic reticulum in all eukaryotic cells, it is hypothesized that they satisfy a requirement which is not met by the members of the hsp70 family. It is our overall goal to determine the functions of these large stress proteins and how they compare to and interact with the hsp7Os. The present proposal will continue our studies of hsp110 and add new studies of grp170. 1) We will determine the role of hsp110 in thermotolerance and define its interactions with other proteins and chaperones in a multi-protein complex which we have observed to exist. 2) We have determined that there are major differences in hsp110 expression in different regions of brain and have noted that these differences parallel susceptibility of these regions to damage resulting from alcohol toxicity, heat stroke, and disease. Therefore, we will define the cellular expression of hsp110 in brain to identify specific cell types, which express high and low levels of hsp110 to relate hsp110 expression to cellular damage occurring in human stress and disease. 3) Finally, we will pursue studies of grpl70, beginning with initial investigations of its in vitro chaperoning characteristics and then examining its in situ functions and associations. These studies will define the functions and characteristics of hsp110 and grp170 and will compare them to one another and to their hsp70 relatives. This work will also shed new light specific brain disorders in which hsp110 may play a primary role.